Silver solder or braze ?

[Eric CoxParticipant @ericcox50497]

Reading the articles in ME, anything and everything appears to be silver soldered. Can’t you braze instead, specifically when building a boiler?.

[Eric CoxParticipant @ericcox50497]

[JasonBModerator @jasonb]

I think there is some brazing in the latest issue

 

I did have a feeling that there was a doubt about the braze material in contact with steam but I may be wrong.

 

Jason

[CirclipParticipant @circlip]

Probably can Eric, but you may want to check with the certification authorities (Boiler Inspectors) first.

 

  If it ain’t broke, why try to fix it??

 

 Regards Ian.

[Chris BParticipant @chrisb73862]

There are 2 issues that I am aware of

 

The first being the composition of the brazing rod, if it was plain brass then as JasonB said there are issues with its contact with the water/steam inside the boiler.

 

The second is the available heating equipment as the temperatures needed for brazing are quite a bit higher than silver soldering temperatures.

 

CB…..

 

 

[JasonBModerator @jasonb]

Just had a read through a couple of back issues and the subject of Dezincification was covered in postbag. This is where the zinc in the braze material is attacked particularly in some water areas.

 

This is again why bronze or gunmetal should be used for boiler bushes etc and not brass.

 

Jason

[Tony MartyrParticipant @tonymartyr14488]

Eric

Quite apart from the metallurgical problems and the extra care required in using a fine, very hot flame, the advantage of silver soldering is that you can flow it throughout a quite large complex shape such as the tube entry into the firebox. The technique of wrapping each tube with thin silver solder wire then putting a large flame onto the ‘back side’ means that when the solder ‘flashes’ every tube is fixed even when they are very close together in the centre of the stack. I wouldn’t like to try that as a brazing operation.

However I think you have to braze the superheater  nose elements but they can be set up in such a way as to be easy to work on.

Tony

[Eric CoxParticipant @ericcox50497]

Thanks for all your comments. The reason I asked was because I had only used silver solder when making jewelry at school and brazing when I was working in the engineering industry.

I was looking at it from a familiarity point of view (more brazing than silver soldering) and from cost.

 

 Cheers Eric 

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